1g 90 awd turbo random shut off 1st crank

[sleeper101]

I have a 1990 awd completely stock, ive been fighting a cold start issue, you could pour some gas down the intake and it would crank and run. ive re -Wired coolant temp sensors, changed ecu, cas, and most recently changed the fuel pump relay under dash by ecu which my understanding is also power for injector. before I could put my noid light on the injector and they would not flash while starting but once u got the car running by priming. it would flash the noid light and car runs great, since ive changed the fuel relay it seems to start better on its own still rough for a few mins but finally runs good. but now im encountering that fuel relay will click and the car will instantly shut off. only when cold does this occur. sometimes it does not do it and sometimes it takes 8 tries to get it cranked. what would cause that relay to click and shut off?

 

[Abe'sGST]

have you changed the fuel filter recently? if not change it and go on from there

 

[sleeper101]

Ya I replaced filter and spark plugs a week ago . its gotta be something electrical IMO.

 

[steve]

since ive changed the fuel relay it seems to start better on its own still rough for a few mins but finally runs good. but now im encountering that fuel relay will click and the car will instantly shut off. only when cold does this occur. sometimes it does not do it and sometimes it takes 8 tries to get it cranked. what would cause that relay to click and shut off?

When that happens does the CEL tun on and stay on? What does the factory boost gauge do?

If you shut off the ignition does the MPI relay turn off right away, after 10 seconds like it should or does it click off and then the car dies?

When you turn the ignition back on the the CEL turn on for 5 seconds and then turn off and boost the factory boost gauge move to 0 and then to -7 while cranking?

 

[sleeper101]

When that happens does the CEL tun on and stay on? What does the factory boost gauge do?

If you shut off the ignition does the MPI relay turn off right away, after 10 seconds like it should or does it click off and then the car dies?

When you turn the ignition back on the the CEL turn on for 5 seconds and then turn off and boost the factory boost gauge move to 0 and then to -7 while cranking?

When the relay clicks, the check engine light flashes and car shuts off immediately . most of the time you can turn ign off and back on and it will cycle normally as if nothing happens, there has been a few times you have to wait a few mins before the relay will work again.

 

[steve]

Sounds like the ECU is crashing but you have to answer the rest of the questions to be sure.

 

[sleeper101]

I didn't get a chance to check it yesterday about the engine light/boost gauge. What would cause ecu to crash and then work again?

 

[steve]

What would cause ecu to crash and then work again?

The most common cause is the factory capacitors leaking. The second most common cause is poor repairs done to fix the capacitors leaking. Much lower on the list is problems with the power going to the ECU like a bad MPI relay or loose/bad battery terminals.

 

[sleeper101]

Ive had both ecu's apart. nothing leaking/burnt/or physical damage could see. im thinking power issue, either ign switch or other issue. sometimes when it shuts off the relay will click several times in a row like a short.

 

[steve]

OK, start with the easy things. Clean and tighten the battery terminals. Try wiggling the wires at the ECU and see if that causes it to shutdown due to a loose terminal. Same at the MPI relay. If you have a spare try swapping it.

If you have good pictures of your ECUs post them. I can't count how many times people have brought me ECUs that looked good to them until I pointed out what was wrong or had a 90 ECU that looked good right up to when C106 shorted from drying out and burned up the ECU.

 

[sleeper101]

Ok I briefly fooled with it tonight. when you crank it over sometimes boost gauge moves to 0 but mostly doesn't move at all. engine light stays on as long as you got the key on. I also noticed a sound coming from bottom of intake when you turn the key to the on position. I assume its something to do with secondary butterfly's? maybe I will get some more time over the weekend to really dig into the issue.

 

[steve]

The sound is likely the ECU trying to home (put the pintle in a known position) the ISC when it first starts.

Still sounds like an ECU problem.

If you just turn the ignition on, the factory boost gauge should more to zero start stay there, the CEL should turn on for 5 seconds and then turn off. You should see a "heartbeat" (on/off repeating) output on the diagnostic connector or it should output fault codes when the CEL remains on. At the same time the ISC should make a clicking/scratching noise as it is homed and then stop.

When you start craning the engine the boost gauge should move to the vacuum area on the gauge while cranking and return to 0 when you stop if the engine didn't start.

 

[sleeper101]

Ok got somewere today. went out this morning. turned key on, boost gauge went to 0 and engine light went off after 5sec. Car fired right up and ran for 5-10 seconds. boom. relay clicked and car shut off. so I pulled ecu and found a leaking capacitor. so I took my old ecu apart and it looked good. so I put it in the car and it fired right up and seems to run good. thanks for the info.

 

[steve]

Glad to hear it. I hope all that other work you did was needed too.

 

[sleeper101]

Ya it was def all needed. now I gotta pull trans cause the pilot bearing seems to of went out. ill get the bugs worked out.

 

[steve]

now I gotta pull trans cause the pilot bearing seems to of went out.

I thought only the automatics had a pilot bearing on these cars and since you own a 90 AWD it not an auto!, what gives?

 

[sleeper101]

I assume it is the pilot bearing or throwout bearing with an issue. when I got the car a few weeks ago and got it running the clutch was froze on it. Put it on my lift in gear running with clutch disengaged and rode the brakes till it free'd up. seemed to work fine for a while. I got nearly 200 miles on it now. But now it wont go in gear unless I crank it in gear and it makes a grinding noise until I let out on clutch. Clutch feels good and the slave was working correctly when I unfroze clutch. but in going to check it all before I pull trans. I use to own this car about 4yrs ago and recently bought it back. its set for a couple yrs. so im just trying to get it back on the road reliable.

 

[Blindmouse]

Sounds for me, it's a typical CAS issue..